Insulation degradation in the field aged MV XLPE power cable - a key concern for utilities - Improvement opportunities

This paper will cover the study carried on service aged MV XLPE cable from Reliance Infrastructure at Wuhan High voltage research Institute, and Dow´s R&D Center in China. Main focus of the study was water treeing in the XLPE insulation. The contamination, protrusion, amber are the initiation points for the degradation of the insulation which ultimately lead to cable failures. 10-13 years service aged three core, 33 kV cables were identified to have water trees. Samples were from the failed section of the field aged cables. In developed geographies proactive preventive analysis of this type is sometimes practiced. Such preventive analysis is one of the effective tools to ensure improvement in utility performance efficiency parameters. Higher the water tree density or longer the water trees, will lead to reduction in AC electrical breakdown strength of the cable and the cable is more prone to the failures, resulting from bridging of the insulation on account of surges from switching or lightening strikes.